Summer fallow and after-planting bermudagrass (Cynodon dactylon) control programs for sugarcane (Saccharum spp. hybrids)

Based on bermudagrass ground cover 2 wk prior to sugarcane planting, tillage plus glyphosate applied postemergence sequentially at 3.4 followed by 2.2 kg ai/ha or a single application at 3.4 kg/ha during the summer fallow period was more effective than tillage alone. Effectiveness of tillage was enhanced when less rainfall was received during the summer fallow period the first year. Rainfall of less than 1 cm 20 d after preemergence application of sulfometuron at 0.2 kg ai/ha in June resulted in 100% bermudagrass ground cover the first year compared with 37% the second year with 15 cm of rainfall during the same period. Terbacil applied after sugarcane planting and metribuzin applied in February resulted in bermudagrass ground cover in May or June of 62% (experiment 1) and 2% (experiment 2) when sulfometuron was used during the fallow period, but no more than 5% when terbacil and metribuzin followed glyphosate plus tillage or tillage alone. In most cases, bermudagrass ground cover at that time was greater when the same glyphosate/tillage treatments were followed by atrazine after planting and pendimethalin plus atrazine in February compared with terbacil after planting and metribuzin in February. When after-planting and February herbicide treatments were applied, sugarcane stalk population, height, and yield each was equivalent regardless of the previous fallow treatment. Nomenclature: Atrazine, 6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine; glyphosate, N-(phosphonomethyl)glycine; metribuzin, 4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one; pendimethalin, N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine; sulfometuron, 2-[[[[(4,6-dimethyl-2-pyrimidinyl)amino]carbonyl]amino]sulfony]benzoic acid; terbacil, 5-chloro-3-(1,1-dimethylethyl)-6-methyl-2,4-(1H,3H)-pyrimidinedione; bermudagrass, Cynodon dactylon (L.) Pers. # 3 CYNDA; sugarcane (Saccharum spp. hybrids) SACCH.